Process of reducing the viscosity of viscous solutions of nitrocellulose and other esters



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Be it known that we, OLOF OAiaLsso'N and Envm THALL, both citizens of the Kingdom of Sweden, and both residents of Stockholm Sweden, have invented anew and useful Process of Reducing the Viscosity of Viscous Solutions of Nitrocellulose and other Esters, of 'whichthe following is a specification.

When dissolving "nitro-cellulose, celluloid, acetyl-cellulose and other esters of cellulose in their solvents, as for instance ether-alcohol, amyl-acetate, ethyl-acetate, acetons and the like, very viscous solutions are obtained which, even in case of a small percentage of dissolved substance, are so thick that they are incapable of flowing. i

Attempts have been made to'prevent said inconvenienceby preparing the cellulose in diflerent manners before the nitration or other chemical treatment. Said methods comprise heating of the cellulose in inert gases, heating the same in an alkaline soluing cellulose prepared in this mannera conpart of the cellulose, besides, always tion and nitration of the cellulose at high temperature. The heating in. inert gases is expensive and difficult to perform from a mechanical point of view, the cellulose frequently being liable to be burnt. On nitratsiderable percentage thereof will always be lost. The heating with alkali is expensive owing to the great. consumption of alkali,

1ssolvin in the alkali-hydrate and thus being lost. 1 oreover, when nitrating such cellulose, a poor output is obtained. Finally, concerning the nitration at high temperature, it is true that a considerable reduction of the viscosity of the dissolved substance may be obtained, but if the nitration be performed at a temperature above 6.,

the apparatus will hardly resistthe acids,"

agreat quantity of the cellulose, besides, dissolving in the hot nitrating being lost.

All of said methods, even if combined and carried to the utmost limit, do not, however, afi'ord' for certain technical purposes any satisfactory result in respect of reduced viscosity.

The object of our present process is to provide means whereby it will be possible to reduce the viscosity of solutions of nitro-' cellulose, celluloid, acetyl-cellulose and other cellulose-esters in their solvents without any acid and Specification of Letters Patent. Patentml Apr .19, 1921.

Application filed December 4, 1919. Serial No. 842,519.

previous preparation of the cellulose used asstarting material in order to reduce the viscosity. By this process for instance easily flowing solutions-of celluloid in amylacetate may be obtained, such solutions otherwise being veryviscous.

We have discovered that solutions of nitro-cellulose and cellulose-esters in their solvents change their viscosity permanently,

when heated. I

The heating may be performed attemperatures within rather wide ranges gen: erally between a temperature of and the temperature at which the esters in question are decomposed. The time of heating will vary with the temperature used and is also dependent on the nature of the material treated and the substance used as solvent for;

is eilected, the more the viscosity is reduced.

Thus a solution of nitro-cellulose in amylacetatehaving the consistency of soft soap will, when heated for an hour to 120 (1.,

be converted into an easily flowin solution' he solu-" having theconsistency of water. tions treated in this mannerdo notundergo anychange as to their properties excepting the viscosity.

By this process an economical reduction of the viscosity of the aforementioned solutions is obtained the pro ct -flowing so easily that it may be filtered t rough a commonfilter and thus liberated from all mechanical impurities, a result of great im portance in most of technical proceedings using such solutions.

ascertained the nature of our said invention and in what manner the same is to be performed, we declare that what we claim is:--,-

1. Process of reducing permanently the viscosity of solutions of cellulose esters, consitting in heating the solutions to a temperature between-60 C. and the temperature l Having now particularly described and vessel toa temperature between 66 C. and

at which the-compound in question is decomposed. 4

2. Process of reducing ermanently the viscosity of solutions of cel ulose esters, consisting in heating the solutions in a closed the temperature at which the-compound in :1 question is decomposed.

' 3. A process for making hi hly concentrated solutions of nitrocell ose having suflieient fluidity to be used as a lacquer or spray, which consists in treating a mixture of nitro-cotton and solvent with heat and pressure.

4. A process for making highly concentrated solutions of nitrocellulose having suflicient fluidity to be used as a lacquer or spray, which consists in treating a mixture of 'nitro-cotton and solvent simultaneously with heat and pressure.

In testimony whereof we have signed ou'ir names. 1 01101 CARLSSONJ EDVIN THALL. 

